Growth,carbohydrates and associated invertase and amylase activities in castor bean and maize as affected by metribuzin and NaCl

Growth parameters (leaf area, length of shoot and root, water content and dry matter accumulation), contents of reducing sugars and saccharose as well as activities of α- and β-amylases of castor bean and maize seedlings and adult plants supplemented with 0.5 μg g^?1 and 2.5 μg g^?1 of metribuzin either alone or in combination with 50 μg g^?1 NaCl, were increased significantly whereas at high concentrations (5 and 10 μg g^?1) of herbicide, an opposite response was apparent. On the other hand, polysaccharide content and invertase activity of castor bean and maize seedlings and adult plants were significantly decreased in response to low concentrations (0.5 and 2.5 μg g^?1) of metribuzin and increased significantly at high concentrations (5 and 10 μg g^?1) of the herbicide either alone or in combination with 50 μg g^?1 NaCl. Total carbohydrate contents of castor bean and maize seedlings and whole plants treated with herbicide either alone or in combination with NaCl did not change significantly. Growth parameters, carbohydrate fractions contents and activities of enzymes in both castor bean and maize seedlings and whole plants treated with herbicide alone were consistently higher than those values detected in plants treated with herbicide in combination with NaCl.     

Effect of Mg,Zn and Mo salts on nitrate reductase activity and soluble protein content in leaves ofQuercus serrata

Leaves ofQuercus serrata seedlings were sprayed with solutions of different concentrations of Mg, Zn and Mo-salts and activity of nitrate reductase (NRA) and soluble protein contents were determined in fresh leaves of different ages. The optimum dose for magnesium sulphate and zinc sulphate was 2.5 mM while for ammonium molybdate it was 0.01 mM. Under optimum doses of these nutrients high levels of NRA and protein contents were maintained upto 28 d of spray. Observations on NRA were further confirmed by leaf direct treatment and excised shoot-dipping experiments which showed maximum NRA at comparatively much lower concentrations of ions than those used for spray.     

In vitro selection and characterization of a callus line ofVigna radiata resistant to NaCl,KCl and Na2SO4

A salt mixture resistant (SMR) cell line ofVigna radiata (L.) Wilczek was isolated by selection on agar solidified PC-L2 medium supplemented with NaCl, KCl and Na₂SO₄ (8∶1∶1) equimolar to 300 mol m^?3 NaCl, a concentration inhibitory to the wild-type non-selected cells (salt mixture sensitive, SMS). This line retained its resistance after subculture for 3 passages (3 months) on normal medium. The SMR line grew significantly better than SMS line at all the levels of salts, though less in saline medium than the SMR on normal medium. The growth of SMR line was significantly higher than that of SMS line under KCl stress. However, both the lines responded similarly to Na₂SO₄ at a concentration higher than 100 mol m^?3. The SMR line was found to be more sensitive to NaCl than SMS line. The SMR line under salt mixture stress maintained lower levels of Na⁺ and higher levels of K⁺ than SMS line. The SMR line failed to regenerate shoots, although rhizogenesis was observed on PC-L2 medium containing salt mixture (300 mol m^?3).     

Effect of NaCl salinity on growth,pigment and mineral element contents,and gas exchange of broad bean and pea plants

Increasing salinity of growth medium induced a reduction in growth and transpiration rate. The concentrations of chlorophylls and carotenoids were increased in most cases in broad bean leaves while in pea plants they remained more or less unchanged with the rise of salinization up to 80mM NaCl. Thereabove a significant decrease in these contents was observed. A stimulation of the net photosynthetic rate of pea was observed at the lowest levels of NaCl but at the highest levels inhibitory effect was recorded. In broad bean all salinization levels inhibited photosynthetic activity, but dark respiration of both plant species was stimulated. The content of Na⁺ in the roots and shoots of both species increased at increasing salinity. In broad bean, Ca²⁺ concentration in shoots and K⁺ and Ca²⁺ contents of roots increased at increasing salinization, while in pea plants, the content of K⁺ and Ca²⁺ was almost unaffected by salinity. Salinity induced an increase in the content of these ions in pea roots. Mg²⁺ content in shoots and roots of both broad bean and pea decreased at increasing salinity except in roots of pea, where it was generally increased.     

Effects of inorganic arsenicals on DNA synthesis in unsensitized human blood lymphocytes in vitro

Effects of inorganic arsenicals on DNA synthesis in unsensitized human blood lymphocytes were biphasic: The chemicals at very low concentrations enhanced DNA synthesis, whereas higher concentrations inhibited DNA synthesis. The concentrations of arsenicals at which the maximum stimulating effect was found were 1×10^?5 M, 1×10^?6 or 2×10^?6 M, and 0.8×10^?6 or 1×10^?6 M for sodium arsenite exposure of 1 h, 3 d, and 6 d, respectively; for sodium arsenate, 1× 10^?5 M, 1×10^?5 M, and 2×10^?6 or 5×10^?6 M, respectively. Arsenicals must be present for the entire 6-d culture period to produce maximum stimulation of DNA synthesis in human lymphocytes. The longer exposure of the lymphocytes to arsenicals, the lower the concentrations of arsenicals at which the maximum stimulating effect on DNA synthesis was found. Stimulating effect of trivalent arsenic (sodium arsenite) on DNA synthesis was stronger than pentavalent arsenic (sodium arsenate), and the stronger the effect of trivalent arsenic than pentavalent, the longer exposure of the cells to the chemicals. Both sodium arsenite and sodium arsenate stimulated DNA synthesis in human lymphocytes to a lower degree than phytohemagglutinin (PHA).     

Changes in growth,osmotic potential and cell permeability of wheat cultivars under salt stress

10-d-old wheat seedlings were grown hydroponically in presence and absence of 100 mM NaCl for 7 d. Salt stress decreased growth of shoots and roots of both cultivars; fresh mass of sensitive cultivar being more affected. NaCl increased membrane permeability to urea, methylurea and ethylurea and decreased membrane partiality in root cortex cells of sensitive cultivar. Neither parameter changed by NaCl in resistant cultivar. NaCl treatment decreased water permeability and osmotic potential in both cultivars; sensitive cultivar was more affected. The results extends our previous data that cell membrane properties are different in salt sensitive and resistant genotypes and so cell permeability could be a potential trait indicating salt tolerance.     

Superoxide dismutase level in response to paraquat and high temperature in the cyanobacteriumGloeocapsa sp

Paraquat (methylviologen) at concentrations above 0.05 mM inhibited the growth of photoautotrophic cyanobacteriumGleeocapsa sp. in axenic cultures. The growth rate was not affected by concentrations of 0.01 mM or less. This concentration resulted after a lag period in a moderate increase in superoxide dismutase level. After removal of paraquat, the cyanobacterium continued to generate higher levels of superoxide dismutase. There was a lag period of one hour before resumption of normal enzyme activity. Addition of puromycin at concentration of 0.5 mg cm^?3 had no effect on cell survival, but greatly enhanced the sensitivity of the culture to the toxicity of paraquat. The data showed an increase of SOD activity by temperatures above the normal growth temperature level. However, this increase was suppressed by chloramphenicol which revealed that the induction of superoxide dismutase by high temperatures was associated withde novo protein synthesis.     

Somatic embryogenesis inCicer arietinum L: Influence of genotype and auxins

Plant regeneration through somatic embryogenesis was obtained in chickpea (Cicer arietinum L.) using immature cotyledons and immature embryonal axes as explants. 2,4-dichlorophenoxyacetic acid (2,4-D), 4-amino-3.5-6-trichloropicolinic acid (picloram) and 3.6-dichloro-0-anisc, acid (dicamba) in concentrations 1, 2, 5, 10 mg dm^?3 were found better than naphthaleneacetic acid (NAA) (10–20 mg dm^?3) for the induction of globular and heart-shaped somatic embryos. The embryos developed upto the dicotyledonary stage on medium supplemented with saccharose, mannitol and silver nitrate (AgNO₃) and developed further into plantlets on medium containing gibberellic acid (GA₃) and abscisic acid (ABA). The frequency of somatic embryogenesis was dependent on the genotype and auxins used.     

Effect of paclobutrazol onin vitro formation of potato microtubers and their sprouting after storage

Paclobutrazol, the gibberellin biosynthesis inhibitor, acceleratedin vitro tuber initiation of potato cv. Rema and increased the uniformity of tuberization period. However, the high concentrations (10–1000 mg l^?1) of this retardant, strongly decreased mass and/or number of microtubers. The microtubers were harvested and stored in darkness (22±2°C) for 250 d. After this period both sprouting and growth of sprouts were affected by previous paclobutrazol treatment.     

Effect of 2,4-dichlorophenoxyacetic acid on nuclear division in stem segments ofPisum sativum L. cultivatedin vitro

We have investigated the influence of 2,4-dichlorophenoxyacetic acid (2,4-D) on the appearance of nuclear fragments, caused by direct nuclear division, as well as on mitotic activity in cultivated internodial stem segments ofPisum sativum L., cv. Bördi, during 180 d of cultivation. Direct nuclear fragmentation (dNF) was indicated by the shape and structure of the nucleus as well as by the occurrence of 1C- and 3C-values of DNA, investigated cytophotometrically. The dNF occurred during the whole cultivation period in segments treated by 2,4-D in concentrations from 4 to 32 mg 1^?1. In the presence of 2 mg 1^?1 of 2,4-D the dNF existed in the explants only up to 90 d. Mitotic activity was not observed in the 2,4-D-free control but occurred during the whole cultivation period when 2,4-D was added in concentrations from 2 to 16 mg l^?1. In the presence of 32 mg l^?1 of 2,4-D the level of mitotic activity was very low at the beginning and ceased after 60 d in culture.     

Uptake,distribution, and turnover rates of selenium in barley

The present communication elucidates initially the topographic distribution of selenium in barley grains. Then by the fluorimetric method the uptake of selenium (selenite) in 8–16 d old germinating barley was estimated. Finally by means of⁷⁵Se the anabolic and catabolic rates (turnover) of⁷⁵Se (selenite) was compared. The distribution of selenium in barley was evaluated after microdissection of barley grains. In dried grains the highest concentration was found in husk and pericarp with about 0.6 ppm Se. Then followed Scutellum with 0.4 and 0.3 ppm in embryon. The aleurone layer, embryonic leaves, and initial root did only have 0.2 ppm Se. In order to know more about the uptake and distribution of selenium in 8-d-old barley, the plants were cultivated for a further 8 d in the culture medium with variation in selenite concentration. In roots and leaves, the uptake did not arrive at saturation during the period studied since the dose-response curve increased up to 0.34 mM selenite in the medium, whereas the selenium levels were about 200 ppm in roots and 30 ppm in leaves. However, the uptake was linear, with concentration during 8 d of cultivation up to 0.84 μM selenite for grain and stem. At higher concentrations the dose-response curve diminished its slope. At 0.34 mM selenite the concentration in grain increased to 6.87 ppm and in the stem to 8.13 ppm. The uptake, distribution, and catabolic rate of selenium components in germinating barley were further evaluated by exposing the plants to 0.0492 μCi⁷⁵Se (12.6 μM selenite) for up to 4 d. Then the plants were moved to a selenium deficient medium for further 4 d. Then finally the medium was supplemented with high doses of cold selenite (0.126 mM selenite) for further 4 d. The first third period made it possible to estimate the rate of uptake. It was highest in roots (313 fmol/h/mg dw), i.e., about 10 times those of grains, stems, and leaves. The intermediate period where the barley was transferred to a selenium deficient medium made it possible to estimate the kinetics and eventual sparing mechanisms. The selenium losses were highest for leaves (39%), then followed by roots and stems (22 and 25%, respectively). The losses were lowest in grain with 9% Se losses. The losses were three times more pronounced during the first day than in the following 3 d. These data may argue that the selenium is distributed into different pools and that sparing mechanisms may be in function. The last period, i.e., the chase experiment, revealed the rate of elimination of selenium under conditions with surplus selenium. The catabolic rate was about 10 times faster in roots (169 fmol/h/mg dw) than in grains and about 8 times faster than in leaves.     

In vitro propagation ofWrightia tinctoria

In vitro method has been developed for propagation ofWrightia tinctoria R.Br. using cotyledonary node segments. Murashige and Skoog's (MS) medium supplemented with 5.0 mg dm^?3 of 6-benzylaminopurine (BAP) and 0.01 mg dm^?3 of naphthaleneacetic acid (NAA) induced up to eight shoots per explant with an average shoot length of 1.4 cm in 21 d. Three fold multiplication rate was achieved during every subculture of regenerated shoots on the same medium producing an average of 230 shoots per node within 84 d. Reduction in BAP concentration from 5.0 to 1.0 mg dm^?3 during subculture promoted shoot length without affecting the rate of multiplication. The differentiated shoots could be rooted by a dip treatment into preautoclaved indole-3-butyric acid (IBA-500 mg dm^?3 for 5 min) followed by their implantation onto MS medium containing 1/4 salts. Rooting was observed within 8–10 d in approximately 80% of shoots inoculated after IBA treatment. 15 d after rooting, the plantlets were transferred to culture bottles containing soil-Soilrite^TM (1∶1) and liquid nutrient solution comprising 1/4 MS salts. After their partial hardening in these bottles for 10 d they were transferred to pots containing soil-Soilrite (1∶1) mixture with 60% transplantation success. Methods are being standardized to improve the rate of survival and large scale field transfer.     

Hormone-like product of vascular tissue stimulating starch accumulation in pith explants of kale and endogenous cytokinins

When stem explants of kale (Brassica oleracea L. var.medullosa), containing pith parenchyma and a strip of vascular tissue, were cultured on simple sucrose medium, a hormone-like factor was transported from the vascular tissue to the adjacent pith, where it stimulated accumulation of starch. Similarly, up to a sevenfold increase of starch content in explants could be induced by cytokinins added to the culture medium. The relative stimulatory effect of several cytokinins (5×10^?6 M) and hormone-like product of vascular tissue (HPVT) in a typical experiment were: control (1.0), trans-zeatin (6.7), HPVT (6.2), N⁶-[2-isopentenyl]adenine (5.4), transzeatin riboside (5.2), N⁶-[2-isopentenyl]adenosine (5.4), kinetin (3.6), 6-benzylaminopurine (3.5), and adenine (2.1). Concentration of endogenous cytokinins was determined using ELISA (trans-zeatin, N⁶-[2-isopentenyl]adenine and their ribosides) andAmaranthus bioassay (total cytokinins). No effect of vascular tissue on the level of endogenous cytokinins in explants was found. The results support the conclusions of previous experiments that the HPVT stimulating starch accumulation is not a cytokinin.     

Restriction endonucleases R.EcoKI and R.EcoR124I are probably located in different environments within the bacterial cell

We describe the phenomenon of a transient state of R124I restriction deficiency after long-term storage of theE. coli[pCP1005] strain at 4°C, or after growth of the culture in synthetic M9 medium with the nonmutagenic solvent dimethyl sulfoxide. The unusual high reversion from the R⁺ ₁₂₄ to the R^? ₁₂₄ phenotype was observed only inE. coli strain transformed with the high-copy number plasmid pCP1005 carryingECoR124IhsdR, M and S genes cloned, but not with strains carrying the natural conjugative plasmid R124. The effect of both treatments on the expression ofEcoR124I phenotype in relation to the possible location of R.EcoR124I restriction endonuclease inE. coli is discussed.     

Interrelationships between vesicular-arbuscular mycorrhiza and rhizosphere microflora in apple replant disease

Phytotoxic micromycetes appear to be responsible for the apple replant disease (ARD). This was suppressed by the inoculation of apple-tree seedlings with some species of vesicular-arbuscular mycorrhizal (VAM) fungi—Glomus fasciculatum andG. macrocarpum. After the inoculation, growth of apple-tree seedlings improved in dependence on the type of soil, on VAM fungus species and on the ARD appearance. After 12-month cultivation, plant biomass (height, shoot and root dry masses) was markedly increased by inoculation withG. fasciculatum. Similarly, the numbers of colony forming units per unit soil (CFU) of phytotoxic micromycetes and of diazotroph bacteria (associative dinitrogen-fixing bacteria) in the rhizosphere was affected; CFU of phytotoxic micromycetes decreased, whereas CFU of the genusAzospirillum was higher. These bacteria could also serve as antagonists against phytotoxic micromycetes. It is also suggested that the ratio of CFU of diazotroph bacteria to CFU of phytotoxic micromycetes can be used as an indicator of the degree of ARD. It may be assumed that the use of some VAM fungi can replace the chemcial treatment of the soil with ARD.     

Studies on lipid oxidation in fish phospholipid liposomes

Fish phospholipid liposomes were prepared and used as an artificial membrane system to study factors influencing-lipid oxidation. The extent of lipid oxidation was indexed by measuring the amount of thiobarbituric acid reactive substances (TBARS) produced. Fe²⁺, Fe³⁺, and Cu²⁺ were potent prooxidants in catalysing lipid oxidation. These metal ions induced lipid oxidation in a dose dependent manner. However, Zn²⁺, Ni²⁺, and Mn²⁺ did not significantly (p>0.05) affect lipid oxidation at all the concentrations (1, 10, or 100 μM) studied. Morin, luteolin (flavonoids), butein (chalcone), tannic acid, ellagic acid (polyphenols), butylated hydroxyanisole (BHA), and butylated hydroxytoluene (BHT) (synthetic antioxidants) were potent antioxidants (producing <50% TBARS compared to control) of Fe²⁺-catalyzed lipid oxidation. Morin, luteolin, and butein possess two hydroxyl substituents, a C₄ ketone structure and a 2–3 double bond, all of which contributed to their antioxidative potential. Fe²⁺ caused some losses of polyunsaturated fatty acids (PUFA), whereas tannic acid protected the oxidation of several of the PUFA including C 16∶1 (Palmitoleic acid), C 18∶3 (Linolenic acid), C 20∶4 (Arachidonic acid), C 20∶5 (Eicosapentaenoic acid), and C 22∶6 (Docosahexaenoic acid).     

Interactions betweenSphagnum mosses and field layer vascular plants in the development of peat-forming systems

The interactions between field layer vascular plants andSphagnum mosses in peat-forming systems are discussed in terms of differences in growth strategies, access to light, acquisition of mineral nutrients and water and the processes involved in the formation of the micro-topographical structures characteristic for these systems. To keep pace with the vertical growth ofSphagnum, the co-occurring vascular plants require a growth strategy involving continuous movement of the growing point and meristematic tissue upwards and a frequent formation of adventitious roots. The growth form and architecture of the vascular plants determine the occurrence and distribution of the structural units on a mire, the hummocks, lawns and hollows. Dwarf shrubs and other vascular plants with an orthotropic growth pattern characterise hummocks, where they form a firm matrix which reinforces and supports the spongy biomass ofSphagnum. In a similar way, clonal herbs stabilise the lawns because of the predominantly plagiotropic, or only weakly orthotropic, growth pattern of the rhizomes and coarse roots in the upper, oxic layers. Extended periods of drought often may have deleterious effects on the mosses but smaller impacts on the vascular plants because of their more efficient water conducting system. Different sources of mineral nutrients are used bySphagnum (atmospheric deposition) and the vascular plants (mineralisation of the organic matter). The presence ofSphagnum, therefore, reduces the supply of nutrient resources to the vascular plants.Sphagnum thereby gains a competitive advantage. A high rate of mineralisation would be beneficial to the vascular plants by increasing their growth rates causing shading of theSphagnum mosses and covering the moss layer by the above-ground litter fall. However, the slow decomposition ofSphagnum litter keeps the system in balance as it will reduce the nutrient supply to the vascular plants.     

Flavin excretion from roots of iron-deficient sugar beet (Beta vulgaris L.)

The characteristics of flavin excretion from iron-deficient sugar-beet roots have been studied. Roots from iron-deficient sugar beet excreted flavins when plants were allowed to decrease the pH of the nutrient solution, but not when plants were grown in nutrient solutions buffered at high pH. As shown by reversed-phase high-performance liquid chromatography, the two major flavins whose excretion was induced by iron deficiency were different from riboflavin, FMN and FAD. These flavins have been identified as riboflavin 3′-sulfate and riboflavin 5′-sulfate by electrospray-mass spectrometry, inductively coupled plasma emission spectroscopy, infrared spectrometry and¹H-nuclear magnetic resonance. We have characterized the time courses of accumulation of the different flavins in the nutrient solution and considered several possible roles for flavin excretion in iron acquisition.     

Osmotic adjustment in leaves ofLycopersicon esculentum andL. pennellii in response to saline water irrigation

Two tomato species (Lycopersicon esculentum andL. pennellii) were grown under unheated plastic greenhouse and irrigated with 0 or 140 mM NaCl. Salinity induces a more important reduction in predawn leaf water potential (ψ_pd) inL. esculentum than inL. pennellii. In both species the osmotic adjustment was achieved by active solute accumulation. The leaf water potential at turgor loss point (ψ_tlp) seemed to be controlled by leaf osmotic potential (ψ_os). The results revealed the existence of limits to the accumulation of osmotic solutes in leaf tissues and the existence of an ontogenetic effect on the solute accumulation. In both species, but essentially inL. pennellii the inorganic solutes contribution especially Na⁺ and Cl^? accumulation to ψ_os was higher than the organic solutes. Therefore, wild species save energy more markedly.